taoensso.sente — com.taoensso/sente 1.16.1

Channel sockets for Clojure/Script.

Protocol  | client>server | client>server ?+ ack/reply | server>user push

• WebSockets: ✓ [1] ✓
• Ajax: [2] ✓ [3]

[1] Emulate with cb-uuid wrapping [2] Emulate with dummy-cb wrapping [3] Emulate with long-polling

Abbreviations:

• chsk - Channel socket (Sente's own pseudo "socket")
• server-ch - Underlying web server's async channel that implement Sente's server channel interface
• sch - server-ch alias
• uid - User-id. An application-level user identifier used for async push. May have semantic meaning (e.g. username, email address), may not (e.g. client/random id) - app's discretion.
• cb - Callback
• tout - Timeout
• ws - WebSocket/s
• pstr - Packed string. Arbitrary Clojure data serialized as a string (e.g. edn) for client<->server comms
• udt - Unix timestamp (datetime long)

Special messages:

• Callback wrapping: [<clj> <?cb-uuid>] for [1], [2]

• Callback replies: :chsk/closed, :chsk/timeout, :chsk/error

• Client-side events: [:chsk/handshake [<?uid> nil[4] <?handshake-data> <first-handshake?>]] [:chsk/state [<old-state-map> <new-state-map>]] [:chsk/recv <ev-as-pushed-from-server>] ; Server>user push [:chsk/ws-ping]

• Server-side events: [:chsk/bad-package <packed-str>] [:chsk/bad-event <event>] [:chsk/uidport-open <uid>] [:chsk/uidport-close <uid>] [:chsk/ws-ping]

Channel socket state map: :type - e/o #{:auto :ws :ajax} :open? - Truthy iff chsk appears to be open (connected) now :ever-opened? - Truthy iff chsk handshake has ever completed successfully :first-open? - Truthy iff chsk just completed first successful handshake :uid - User id provided by server on handshake, or nil :handshake-data - Arb user data provided by server on handshake :last-ws-error - ?{:udt _ :ev <WebSocket-on-error-event>} :last-ws-close - ?{:udt _ :ev <WebSocket-on-close-event> :clean? _ :code _ :reason _} :last-close - ?{:udt _ :reason _}, with reason e/o #{nil :requested-disconnect :requested-reconnect :downgrading-ws-to-ajax :unexpected} :udt-next-reconnect - Approximate udt of next scheduled auto-reconnect attempt

Notable implementation details:

• core.async is used liberally where brute-force core.async allows for significant implementation simplifications. We lean on core.async's efficiency here.
• For WebSocket fallback we use long-polling rather than HTTP 1.1 streaming (chunked transfer encoding). Http-kit does support chunked transfer encoding but a small minority of browsers &/or proxies do not. Instead of implementing all 3 modes (WebSockets, streaming, long-polling) - it seemed reasonable to focus on the two extremes (performance + compatibility). In any case client support for WebSockets is growing rapidly so fallback modes will become increasingly irrelevant while the extra simplicity will continue to pay dividends.

General-use notes:

• Single HTTP req+session persists over entire chsk session but cannot modify sessions! Use standard a/sync HTTP Ring req/resp for logins, etc.
• Easy to wrap standard HTTP Ring resps for transport over chsks. Prefer this approach to modifying handlers (better portability).

[4] Used to be a csrf-token. Was removed in v1.14 for security reasons. A nil remains for semi-backwards-compatibility with pre-v1.14 clients.

ajax-call cljs

DEPRECATED: Please use ajax-lite instead

ajax-lite cljs

Alias of taoensso.encore/ajax-lite

as-event clj/s

(as-event x)

assert-event clj/s

(assert-event x)

Returns given argument if it is a valid [ev-id ?ev-data] form. Otherwise throws a validation exception.

cb-error? cljs

(cb-error? cb-reply-clj)

cb-success? cljs

(cb-success? cb-reply-clj)

ChAjaxSocket cljs

ChAutoSocket cljs

chsk-connect! clj/s

(chsk-connect! chsk)

chsk-destroy! clj/s

Deprecated

chsk-disconnect! clj/s

(chsk-disconnect! chsk)

chsk-reconnect! clj/s

(chsk-reconnect! chsk)

Useful for reauthenticating after login/logout, etc.

chsk-send! clj/s

(chsk-send! chsk ev)

(chsk-send! chsk ev opts)

(chsk-send! chsk ev ?timeout-ms ?cb)

Sends [ev-id ev-?data :as event], returns true on apparent success.

ChWebSocket clj/s

client-event-msg? clj/s

(client-event-msg? x)

debug-mode?_ clj/s

default-chsk-url-fn cljs

DEPRECATED

EdnPacker cljs

event-msg? clj/s

event? clj/s

(event? x)

Valid [ev-id ?ev-data] form?

IChSocket clj/s protocol

-chsk-connect! clj/s

(-chsk-connect! chsk)

-chsk-disconnect! clj/s

(-chsk-disconnect! chsk reason)

-chsk-reconnect! clj/s

(-chsk-reconnect! chsk)

-chsk-send! clj/s

(-chsk-send! chsk ev opts)

make-channel-socket! clj/s

Platform-specific alias for make-channel-socket-server! or make-channel-socket-client!. Please see the appropriate aliased fn docstring for details.

make-channel-socket-client! clj/s

(make-channel-socket-client!
  path
  ?csrf-token
  &
  [{:keys [type protocol host port params headers recv-buf-or-n packer
           ws-kalive-ms client-id ajax-opts wrap-recv-evs? backoff-ms-fn]
    :as opts
    :or {type :auto
         recv-buf-or-n (async/sliding-buffer 2048)
         packer :edn
         client-id (or (:client-uuid opts) (enc/uuid-str))
         wrap-recv-evs? true
         backoff-ms-fn enc/exp-backoff
         ws-kalive-ms (enc/ms :secs 20)}} _deprecated-more-opts])

Returns nil on failure, or a map with keys: :ch-recv ; core.async channel to receive event-msgs (internal or from ; clients). May put! (inject) arbitrary events to this channel. :send-fn ; (fn [event & [?timeout-ms ?cb-fn]]) for client>server send. :state ; Watchable, read-only (atom {:type _ :open? _ :uid _ :csrf-token _}). :chsk ; IChSocket implementer. You can usu. ignore this.

Common options: :type ; e/o #{:auto :ws :ajax}. You'll usually want the default (:auto). :protocol ; Server protocol, e/o #{:http :https}. :host ; Server host (defaults to current page's host). :port ; Server port (defaults to current page's port). :params ; Map of any params to incl. in chsk Ring requests (handy ; for application-level auth, etc.). :headers ; Map of additional headers to include in the initiating request ; (currently only for Java clients). :packer ; :edn (default), or an IPacker implementation. :ajax-opts ; Base opts map provided to taoensso.encore/ajax-lite. :wrap-recv-evs? ; Should events from server be wrapped in [:chsk/recv _]? :ws-kalive-ms ; Ping to keep a WebSocket conn alive if no activity ; w/in given msecs. Should be different to server's :ws-kalive-ms.

make-channel-socket-server! clj/s

(make-channel-socket-server!
  web-server-ch-adapter
  &
  [{:keys [recv-buf-or-n ws-kalive-ms lp-timeout-ms send-buf-ms-ajax
           send-buf-ms-ws user-id-fn bad-csrf-fn bad-origin-fn csrf-token-fn
           handshake-data-fn packer allowed-origins authorized?-fn
           unauthorized-fn ?unauthorized-fn]
    :or {ws-kalive-ms (enc/ms :secs 25)
         send-buf-ms-ws 30
         allowed-origins :all
         lp-timeout-ms (enc/ms :secs 20)
         csrf-token-fn
           (fn [ring-req]
               (or (:anti-forgery-token ring-req)
                   (get-in ring-req [:session :csrf-token])
                   (get-in ring-req
                           [:session
                            :ring.middleware.anti-forgery/anti-forgery-token])
                   (get-in ring-req [:session "__anti-forgery-token"])))
         packer :edn
         unauthorized-fn (fn [_ring-req]
                             {:status 401 :body "Unauthorized request"})
         send-buf-ms-ajax 100
         bad-origin-fn (fn [_ring-req]
                           {:status 403 :body "Unauthorized origin"})
         handshake-data-fn (fn [ring-req] nil)
         user-id-fn (fn [ring-req] (get-in ring-req [:session :uid]))
         recv-buf-or-n (async/sliding-buffer 1000)
         bad-csrf-fn (fn [_ring-req] {:status 403 :body "Bad CSRF token"})}}])

Takes a web server adapter[1] and returns a map with keys:

:ch-recv ; core.async channel to receive event-msgs (internal or from clients). :send-fn ; (fn [user-id ev] for server>user push. :ajax-post-fn ; (fn [ring-req]) for Ring CSRF-POST + chsk URL. :ajax-get-or-ws-handshake-fn ; (fn [ring-req]) for Ring GET + chsk URL.

:connected-uids ; Watchable, read-only (atom {:ws #{} :ajax #{} :any #{}}). :send-buffers ; Implementation detail, read-only (atom {:ws #{} :ajax #{} :any #{}}).

Security options:

:allowed-origins ; e.g. #{"http://site.com" ...}, defaults to :all. ; Alpha

:csrf-token-fn ; ?(fn [ring-req]) -> CSRF-token for Ajax POSTs and WS handshake. ; CSRF check will be skipped iff nil (NOT RECOMMENDED!).

:authorized?-fn ; ?(fn [ring-req]) -> When non-nil, (authorized?-fn <ring-req>) ; must return truthy, otherwise connection requests will be ; rejected with (unauthorized-fn <ring-req>) response. ; ; May check Authroization HTTP header, etc.

:?unauthorized-fn ; An alternative API to authorized?-fn+unauthorized-fn pair. ; ?(fn [ring-req)) -> <?rejection-resp>. I.e. when return value ; is non-nil, connection requests will be rejected with that ; non-nil value.

Other common options:

:user-id-fn ; (fn [ring-req]) -> unique user-id for server>user push. :handshake-data-fn ; (fn [ring-req]) -> arb user data to append to handshake evs. :ws-kalive-ms ; Ping to keep a WebSocket conn alive if no activity ; w/in given msecs. Should be different to client's :ws-kalive-ms. :lp-timeout-ms ; Timeout (repoll) long-polling Ajax conns after given msecs. :send-buf-ms-ajax ; [2] :send-buf-ms-ws ; [2] :packer ; :edn (default), or an IPacker implementation.

[1] e.g. (taoensso.sente.server-adapters.http-kit/get-sch-adapter) or (taoensso.sente.server-adapters.immutant/get-sch-adapter). You must have the necessary web-server dependency in your project.clj and the necessary entry in your namespace's ns form.

[2] Optimization to allow transparent batching of rapidly-triggered server>user pushes. This is esp. important for Ajax clients which use a (slow) reconnecting poller. Actual event dispatch may occur <= given ms after send call (larger values => larger batch windows).

sente-version clj/s

Useful for identifying client/server mismatch

server-event-msg? clj/s

(server-event-msg? x)

set-logging-level! clj/s

DEPRECATED. Please use timbre/set-level! instead

start-chsk-router! clj/s

Platform-specific alias for start-server-chsk-router! or start-client-chsk-router!. Please see the appropriate aliased fn docstring for details.

start-chsk-router-loop! clj/s≠

clj

(start-chsk-router-loop! event-msg-handler ch-recv)

cljs

(start-chsk-router-loop! event-handler ch-recv)

DEPRECATED: Please use start-chsk-router! instead

start-client-chsk-router! clj/s

(start-client-chsk-router! ch-recv
                           event-msg-handler
                           &
                           [{:as opts :keys [trace-evs? error-handler]}])

Creates a simple go-loop to call (event-msg-handler <server-event-msg>) and log any errors. Returns a (fn stop! []). Note that advanced users may prefer to just write their own loop against ch-recv.

Nb performance note: since your event-msg-handler fn will be executed within a simple go block, you'll want this fn to be ~non-blocking (you'll especially want to avoid blocking IO) to avoid starving the core.async thread pool under load. To avoid blocking, you can use futures, agents, core.async, etc. as appropriate.

start-server-chsk-router! clj/s

(start-server-chsk-router!
  ch-recv
  event-msg-handler
  &
  [{:as opts :keys [trace-evs? error-handler simple-auto-threading?]}])

Creates a simple go-loop to call (event-msg-handler <server-event-msg>) and log any errors. Returns a (fn stop! []). Note that advanced users may prefer to just write their own loop against ch-recv.

Nb performance note: since your event-msg-handler fn will be executed within a simple go block, you'll want this fn to be ~non-blocking (you'll especially want to avoid blocking IO) to avoid starving the core.async thread pool under load. To avoid blocking, you can use futures, agents, core.async, etc. as appropriate.

Or for simple automatic future-based threading of every request, enable the :simple-auto-threading? opt (disabled by default).

validate-event clj/s

(validate-event x)

Returns nil if given argument is a valid [ev-id ?ev-data] form. Otherwise returns a map of validation errors like {:wrong-type {:expected _ :actual _}}.